1. (Field of Technology)
The present invention relates to a mount for the support thereon of dielectric coaxial resonators such as those used in, for example, a microwave filter or the like.
2. (Description of the Prior Art).
A commerically available dielectric coaxial resonator 1, which may be for example, a quarter-wavelength coaxial TEM resonator, is shown in FIG. 1 of the accompanying drawings. The resonator 1 has a dielectric body 4 made of, for example, a ceramic material of the titanium oxide type which is filled between inner and outer conductors 2 and 3. More specifically, the coaxial TEM resonator 1 comprises a tubular dielectric body 4 having a relatively great wall thickness. The inner and outer peripheral surface of the body 4 have , for example, a silver paste, which is excellent in high frequency conductivity and also in bondability, applied and baked thereon to form the inner and outer conductors 2 and 3, respectively. A hollow is defined inside the inner conductor 2, into which hollow an elongated center rod 5 made of a similar ceramic material and having a length greater than the axial length of the dielectric body 4 is either inserted or fixed, depending on the needs, with one end 6 of said center rod 5 protruding outwardly from an open end face 7 of the resonator 1. That end 6 of the center rod 5 is coated, or otherwise covered, with an electrode layer 8 which is a continuation of the inner conductor 2. At the opposite end of the resonator 1 remote from the projecting end 6, the inner and outer conductors 2 and 3 are electrically connected together by means of an electrode 9.
Another commercially available resonator 11, which does not make use of the center rod 5, is partially shown in FIG. 2 of the accompanying drawings. The resonator 11 shown in FIG. 2 is provided with a terminal electrode 12 of any desired shape which is inserted into, and fixed by a deposit of an electroconductive bond material in, the hollow of the inner conductor 2, and electrically connected with the inner conductor 2. Where the resonator 11 is to be coupled with other electrtic components, for example, to be capacitively coupled with other resonators or connectors, chip capacitors 21 and 22 are used. Specifically, one end of the terminal electrode 12 protruding outwardly from the resonator 11 is machined to any desired shape, and first electrodes 23 and 24 of the respective capacitors 21 and 22 are connected to the machined end of the terminal electrode 12, the other electrodes 25 and 26 of the respective capacitors 21 and 22 being connected with the other resonators or connectors by way of respective lead lines 27 and 28.
When a microwave filter is assembled, a plurality having dielectric coaxial resonators 1 or 11 of the construction shown in FIG. 1 or 2, respectively, are aggregated together on a common support. More specifically, as shown in FIG. 3, which shows to the use of the dielectric coaxial resonators 1 having the construction shown in FIG. 1, the support, for supporting the coaxial resonators 1 to complete the microwave filter, is constituted by a grounded plate 31. The coaxial resonators 1 are mounted on the grounded plate in side-by-side fashion with their outwardly protruding ends 6 positioned on one side of the aggregation of the coaxial resonators 1. When they soldered to the grounded plate 31, with solder deposits 32 connecting firmly a portion of the outer conductor 3 of each coaxial resonator 1 to the grounded plate 31. Each two neighboring coaxial resonators 1 are also soldered together by a respective solder deposit 33 to provide a secure connection between the outer conductors 3 of the neighboring coaxial resonators 1.
When a microwave filter is assembled with the use of the coaxial resonators 11 having construction shown in FIG. 2, the coaxial resonators 11 are mounted and connected in a manner identical to that described with reference to and shown in FIG. 3.
Since each of the coaxial resonators 1 and 11 hitherto utilized is cylindrical in exterior shape, the coaxial resonators 1 or 11 when mounted on the grounded plate 31 define a line contact, not a surface contact, between each two coaxial resonators . The problem has often occurred of an insecurely fixing one or more of the coaxial resonators 1 or 11 to the grounded plate 31. In order to ensure rigid fixing, it has been suggested to use elastic pieces (not shown) between the coaxial resonators 1 or 11 and the grounded plate 31, or to form spring catches in a portion of the grounded plate 31, so that the coaxial resonators 1 or 11 can be fixed within an enclousre (not shown) while the outer conductors 3 of the respective coaxial resonators 1 or 11 are urged by the elastic pieces or the spring catches in the grounded plate 31, as disclosed in, for example, Japanese Laid-open Utility Model Publication No. 59-171401, published in 1984.
According to the suggested versions, special machining and/or molding is required to form the elastic pieces and the spring catches in the grounded plate 31, resulting in the increased cost of manufacture of the microwave filter as a whole.
Moreover, the presence of the solder deposit 33 between each two neighboring coaxial resonators 1 or 11 has been found to pose a problem in that, depending on the amount of solder used to form each solder deposit 33, the resultant microwave filter is susceptible to changes in operating characteristics to such an extent as to render difficult the adjustment of the operating characteristics thereof.